Use of petroleum as a main energy source has generated air pollutants and green gas, resulting in recent severe environmental problems. To solve these, Kyoto Protocol was signed internationally for the purpose of regulation of carbon dioxide, a typical global warming material. Then, Korea has been included in the countries subjected to such regulation since 2013.
Under these circumstances, many attentions have been given to separation technologies for carbon dioxide. Main separation technologies for carbon dioxide that have been developed to date include pressure swing adsorption, water scrubbing, methanol scrubbing, polyethylene glycol scrubbing, membrane separation, cryogenic liquefaction, etc.
Membrane separation is a gas separation method using a separation membrane to allow a specific ingredient to permeate therethrough selectively. Such gas separation using a separation membrane performs gas separation through dissolution and diffusion, involves no phase change, and requires low energy consumption and a small area for installation to facilitate control and maintenance. By virtue of such advantages, many attentions have been given to membrane separation. In such a membrane separation method, a polymeric membrane has been used frequently. A commercially available separation membrane for carbon dioxide has a problem of trade-off between selectivity and permeability, because permeability is low when selectivity is high and selectivity is low when permeability is high, and shows disadvantages of low physical strength, chemical stability and temperature resistance.
Various polymeric composite membranes have been developed to overcome such problems. For example, a known technological process uses a polymeric separation membrane. However, the technological process requires maintenance of low temperature and provides low selectivity to carbon dioxide, and thus is not amenable to commercialization (Patent Document 1).
Meanwhile, it is known that a method including interfacial polymerization of polyimide onto a polymeric composite membrane increases carbon dioxide/hydrogen selectivity. However, the above method does not provide permeability and selectivity sufficient for commercialization (Patent Document 2).